This invention relates to cursor control devices in particular to cursor control devices useful in interactive, display oriented computer systems wherein a display cursor is movable about the screen of the device by means of the cursor control device.
Over the past decade or so, different functional control devices for use with computer display systems have been developed along with the rapid development of such systems and so called "smart" display terminals. These devices have taken several forms, such as joy sticks, light pens, touch panels and hand held cursor control devices, commonly referred to as a "mouse". One of the most prevalent uses of these devices is to alter the display at selected locations by controlling a display cursor which is selectively moved over the display by means of the cursor control device.
The mouse, in particular, has become one of the most popular of the pointing devices used with interactive, display oriented computer systems, to control the visual cursor on the system display. The mouse tracks the movement of a user's hand as the user moves the mouse about on a work surface or pad usually next to the user's keyboard input to the system. Microswitches may be positioned on the top surface of the housing of the mouse to perform various functions in the system upon finger operation of a microswitch selected by the user. The mouse has recently become available in the office products market as a part of the 8010 Professional Workstation, developed, manufactured and distributed by Xerox Corporation.
Cursor research and development over this period of time has led many to conclude that the concept of the mouse is the preferred and best means for performing cursor function controls, some of the reasons being its adaptability for use in conjuction with a keyboard input of such systems from a human engineering standpoint and ease of display cursor movement with desired functions implemented by microswitches present on the mouse.
The "mouse" type of cursor control devices employed to date have been of electromechanical design. Examples of such devices may be found in U.S. Pat. Nos. 3,304,434; 3,541,541; 3,835,464; 3,892,963 and 3,987,685. The best known electromechanical "grandfather" mouse was developed at Standford Research Institute and is disclosed in U.S. Pat. No. 3,541,541. This mouse employs a pair of wheels that turn potentiometer shafts to encode X and Y motion into analog signals. Each wheel turns as the mouse is moved along its respective coordinate direction and slips sideways as the mouse is moved in an orthogonal direction. When the mouse is moved diagonally, both wheels turn and slip simultaneously. The design of this mouse led to the use of ball beatings as wheels and optical shaft encoders to generate a two bit quadrature signalling code, as disclosed in U.S. Pat. No. 3,892,963. The motion of a wheel caused a two bit output for a coordinate direction to form square waves in quadrature, with phase and frequency determining the direction and speed of travel. Each bit transition represented motion of one resolvable step which was employed to move the cursor on the display screen. Further development led to the employment of a ball or sphere instead of two wheels for more uniform tracking (U.S. Pat. Nos. 3,835,464 and 3,987,685). Internally, the sphere itself was a trackball with shafts turning against the ball and with commutation as shaft encoders or optical disc encoders, the latter being disclosed in U.S. Pat. No. 3,304,434.
While these mice have proved to be quite useful in performing display functions, they have not been outstandingly reliable, particularly over long periods of use. For example, the mechanical moving parts of the mouse, such as the balls and wheels, become dirty and slip on the work surface or pad, rather than provide continuous rolling action, or the commutators become dirty and skip.
Also, because of the precision and tolerances necessary for the mechanical moving parts and the number of parts involved, these mechanical mice have been expensive to fabricate.
The goal, therefore, is to design a mouse with no moving parts (excluding the microswitches) thereby eliminating the above mentioned mechanical disadvantages and providing a mouse with high reliability over long periods of time. One direction toward the goal of no moving parts is optics and optical detection of mouse tracking functions. The concept of optical tracking, i.e., optical detection of an optical image, such as a track, lines, bars or grating, is not new. Examples of such tracking utilizing one or more optical detectors are disclosed in U.S. Pat. Nos. 3,496,364; 3,524,067; 4,114,034 and 4,180,704. However, none of these optical tracking devices disclose optical tracking techniques suitable to perform the functions required in a mouse, i.e., they are not "smart" enough to provide multidirectional tracking indicative of direction of movement and the amount of that movement necessary for a display oriented computer system.